Magnetic structure



7 Nov. '17, 1931. FISCHER 1,832,290

MAGNETIC STRUCTURE Filed Jan. 14, 1951 FIG.

INVENTOR E. FISCHER ,4 TTORNEY Patented Nov. 17, 1931 UNITED STATES PATENT OFFICE ERNST FISCHER, OF BERLIN-LICHTERFELDE, GERMANY, ASSIGNOR TO SIEMENS & HALSKE AKTIENGESELLSCHAFT, OF SIEMENSSTADT, NEAR BERLIN, GERMANY, A

CORPORATION OF GERMANY MAGNETIC STRUCTURE Application filed J'anuary 14, 1931, Serial No. 508,582, and in Germany February 25, 1930.

The invention relates in general to magnetic structures such as magnetic cores and more particularly to cores for loading coils for communication circuits.

There has been used in the past for inductance devices in communication circuits cores of powdered magnetic material combined with insulating and binding materials, formed into the desired shapes by means of pressure. I have frequently been used. The application of the winding to an annular shaped core is more diificult than for open-ended cores. The manufacture of'annular coils in two or more parts which, after the windings are applied thereto, are connected together to form the annular shaped coil, has been proposed. The use of a divided core produces an unavoidable air gap which is transverse to the direction of the magnetic lines of force and in some cases this air gap adversely aifccts the magnetic propertiesof the completed coil.

In connection with certain types of loading coils, in which it is desirable to have a short flux path, the so-called shell type core has been used. In loading coils employing shell type cores the windings are placed in the interior of the core in such a manner that the core material practically encloses the wlndings. With this type of coil having a core of powdered magnetic material, it is necessary that thecore be molded in two or more parts. The core parts are fastened together after the insertion of the winding. In this type of coil the divided core also produces an unavoidable air gap which is transverse to the direction of the magnetic line of force and which adversely affects the magnetic properties of the completed coil.

It has also been found that in the course of time the air gap will change due to the aging of the molded magnetic material and to strains in the material due to the application of the winding and possibly other causes. The change in the length of the air gap changes the magnetic properties of the coil and the stray magnetic field at theair gap. These variations, especially in the case of loading coils, adversely affect the functioning of the coils in the circuits for which they Cores having an annular shape.

were designed, particularly as these variations cannot be compensated for in the original design of the coil.

The principal object of the invention is to overcome or greatly reduce these disadvantages in the use of magnetic cores having air gaps transverse to the direction of the mag netic lines of force. Other and related objects of the invention will be apparent from the following description.

A feature of the invention comprises the use of one or more layers of a magnetic material of high permeability at the connecting surfaces of the core sections so that the connecting layers of the magnetic material l1aving a high permeability are in contact at a sufliciently' large number of points.

As the layers of magnetic material having ahigh permeability are in contact at a large number of points they will not present any substantial resistance to the magnetic lines of force from one section of the core to the adjacent section.

Even where small variations in the shape of the core occur due to the aging of the molded magnetic material, a suflicient number of contactlng surfaces still remain between the layers of magnetic material having the high permeability so that no substantial variation in the electrical characteristics of the coil will take place. 111 order to avoid eddy currents in these layers of high permeability they can be made as thin as desired and subdivided in the manner well-known in the prior art.

Another feature of the invention is the use of a thin layer of magnetic material having a high permeability to cover the outer surface of the molded magnetic core to avoid the injurious effects of stray magnetic fields at the outer surface of the core.

The invention will be better understood by reference to the following description and accompanying drawings in which,

Figs. 1 and 2 are different embodiments of the invention.

The loading coil shown in Fig. 1 comprises two halves, l and 2, of the shell type core of magnetic molded material, the coil windings 3 on the interior of the shell type core and layers of magnetic material of high permeability 4 and 5 assembled between the halves 1 and 2 of the shell type core. The layers of magnetic material 4 and 5 are preferably of sheet permalloy. The layers of sheet permalloy 4 and 5 can be fastened to the molded core halves 1 and 2 after these halves have been completely molded or they can be securely fastened to the halves in the molding operation and molded integral therewith. An alternate method of applying the thin layers of the magnetic material of high permeability to the molded core parts would be by applying this material to the separating surfaces or to the entire surfaces of the parts 1 and 2 by electrolytic means.

The embodiment in Fig. 2 shows a coil comprising windings 17 and 18 wound on an annular core of magnetic material which is made up of the two halves 11 and 12. At the contacting surfaces of the two halves of the cores 11 and 12, layers 13, 14. and 15, 16' of magnetic material having a high permeability are applied for reducing the effects of these air gaps between two 'halves of the molded cores 11 and 12. These layers 13,14 and 15, 16 can be applied to the core halves 11 and 12 in the same manner as that referred to above in connection with Fig. 1.

Although for the purposes of explaining the invention, it has been described in connection with certain specific arrangements, the principles involved are capable of general applications to arrangements not specifically described but which will readily occur to persons skilled in the art, which are included within the scope of the appended claims.

What is claimed is:

1. A magneticrore having subdivisions transverse to the direction of the magnetic lines of force, characterized in that a substance having a permeability higher than that of the core material is applied on the dividing surfaces of the core subdivisions.

2. A magnetic core having subdivisions transverse to the direction of the magnetic linesof force, and a substance having a higher permeability than that of the core material on the dividing surfaces of the core subdivisions, characterized in that the substance having the higher permeability is applied to the dividing surfaces by electrolytic means.

3. A magnetic core having subdivisions transverse to the direction of the magnetic lines of force, and a substance having a higher permeability than that of the core material on the dividing surfaces of the core subdivisions, characterized in that the substance having the higher permeability comprises thin laminations of permalloy.

4. A magnetic core having subdivisions transverse to the direction of the magnetic lines of force, and a substance having a higher permeability than that of the core material on the dividing surfaces of the core subdivisions, characterized in that the substance having the higher permeability comprises thin laminations molded integral with said core subdivisions.

5. A magnetic core havin subdivisions transverse to the direction 0 the magnetic lines of force and a substance having a higher permeability than that of the core material on the dividing surfaces of the core subdivisions, characterized in that the outer surface of the core is covered with a thin layer of material having a higher permeability than that of the core material.

In witness whereof, I hereunto subscribe my name this 18th day of December 1930.

ERNST FIsoHER. 

